Question

Researchers noted that about half of all species of bacteria contain small segments of DNA of about 20-50 base pairs derived from plasmids or viruses. The phrase clustered regularly interspaced short palindromic repeats (CRISPR) describes the organization of these viral DNA segments in the bacterial genome. Bacteria use CRISPR to: (Select all that apply.)
"remember" the first time it was infected with a virus.

identify viral DNA by complementary base pairing with RNA.

transcribe RNA that combines with a protein that has a DNA-cleaving function.

transcribe RNA that combines with a protein that has a RNA-cleaving function

identify viral DNA by complementary base pairing with template DNA.

Answer 1

The correct answers are:  

• transcribe RNA that combines with a protein that has a DNA-cleaving function.  

• identify viral DNA by complementary base pairing with template DNA.

CRISPR is a DNA sequence found in bacteria (or other prokaryotic cell), derived from DNA fragments from viruses that have previously infected that bacteria. Bacteria use CRISPR to destroy DNA from next similar viruses. So, it is form of antiviral defense in bacteria.

Cas9  is an RNA-guided DNA endonuclease enzyme (DNA-cleaving function) associated with the CRISPR that cleave specific sequences of DNA complementary to the CRISPR sequence.